Toy building block



FIG. 1 is a top perspective view of a toy building block showing my new design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a top perspective view of a modified form of the design shown in FIGS. 1 and 2;

FIG. 4 is a bottom perspective view thereof;

FIG. 5 is a front elevational view thereof; and

FIG. 6 is a rear elevational view of the design shown in FIGS. 1 and 2. 

The ornamental design for a toy building block, as shown and described. 